Lithium-ion cells have recently been widely used as large-capacity cells. However, because the lithium-ion cells have a mechanism in which graphite or the like is used for an anode electrode and they are operated by inserting and desorbing lithium ions into and from the negative electrode, it is generally pointed out that they may cause precipitation of metal lithium and therefore still have a safety problem.
It is known, as a method for avoiding this problem, to use lithium titanate represented by Li1.33Ti1.66O4, LiTi2O4 or others as a material for the negative electrode. Lithium titanate has a voltage of 1.5 V in terms of lithium, exhibits substantially no change in crystal structure resulting from charging and discharging, and therefore has been drawing attention as an electrode material having good safety and service life.
Meanwhile, in order to enhance the cell characteristics, particularly the power output characteristic, various types of development have been made, such as a technique in which lithium titanate is finely ground and an electrode with the ground lithium titanate carried on carbon is used.
Patent Literature 1 proposes lithium titanate fine particles obtained by subjecting a powder mixture of a titanium compound and a lithium compound to heat treatment.